Volume 1, Issue 6 (November 1973)

One-Dimensional Consolidation of Retarded Plastic Concrete

A study of the one-dimensional consolidation of plastic concrete (that is, a concrete mix within the first few hours after mixing when it can still be remolded) is discussed with particular reference to the soil mechanics analogy which the author proposed for a wider study of some engineering properties of plastic concrete [2]. This property of the mix is discussed in terms of classical consolidation parameters used in soil mechanics, namely the coefficient of compressibility (mv) and the coefficient of consolidation (cv. It was desired to study the consolidation behavior of the material as it is just after mixing and, consequently, the mixes were retarded by the addition of small quantities of sugar to minimize the effect of hydration.

Theoretical equations are developed to express the dependence of these two quantities on the initial moisture content of the mix and the applied consolidation pressure.

A linear relationship, as predicted from theory, was obtained between mv and the initial moisture content from results of the laboratory study in which the Rowe's cell was used. Further empirical results showed that there is no apparent simple relationship between cv and initial moisture content. However, there is a linear relationship between cv and pressure increment. The mv values lie between 1.25 × 10−3 and 6.25 × 10−2 in.2/lb, while the cv values lie between 1.5 × 10−2 and 4.5 × 10−2 in.2/min. In general, the mixes tested behaved similarly to remolded clays.

The Darcy coefficient of permeability of the mixes, deduced from the consolidation data, is of the order of 10−8 cm/s.